JP2003278869A - Rolling element for traction drive and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rolling element for traction drive having superior characteristics for traction, which is developed without secular change, and also to provide a manufacturing method therefor. <P>SOLUTION: In the rolling elements for traction drive, a driving force is transmitted by means of traction oil between rolling contact surfaces. Referring to fine profile on the rolling-contact surfaces of either one of rolling elements on the drive side or rolling elements on the driven side, recesses of grooves and projections of ridges are alternately given on the surfaces of the rolling elements. The rolling-contact surfaces of the other rolling elements are made smooth. If the surface hardness of the rolling parts in the rolling elements on the one side is taken as Hx, and the surface hardness of the rolling parts in the other rolling elements on the other side is taken as Hy, Hx>Hy is held in the rolling elements. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a traction drive roller used in a power transmission device such as an automobile or an industrial machine for continuously rotating a rotation of an input shaft by a traction drive and transmitting the rotation to an output shaft. The present invention relates to a moving body and a manufacturing method thereof.

[0002]

2. Description of the Related Art Continuously variable transmissions have been studied in various fields because they have excellent power transmission performance and do not generate shift shocks. Among them, for the purpose of transmitting a large amount of power, a system of transmitting power between rolling surfaces via traction oil (traction drive system: rolling system) has been studied.

The traction drive system, in which power is transmitted between rolling surfaces via traction oil, has a mechanism applicable to high-power engines. For example, a traction drive type continuously variable transmission 1 shown in FIG. 1 is a metal rolling element that comes into contact with traction oil, that is, two discs (an input disc 3 fixed to an input shaft 2 and an output disc 4 fixed to the input shaft 2). By changing the inclination of the roller shaft of the power roller 6 sandwiched between the output discs 5) and changing the contact radius of both the discs 3 and 5 via the power roller 6, power is transmitted in a continuously variable speed. Is configured. One example of this traction drive type continuously variable transmission is a half toroidal type continuously variable transmission. The rolling elements (input disk 3, output disk 5 and power roller 6) used in such a traction drive system are required to have excellent traction characteristics under high temperature and high surface pressure and high rolling contact fatigue life performance.

In addition, considering the reduction of the load on the environment in the future,
In order to further improve fuel efficiency, it is necessary to reduce the weight of the vehicle, and for this purpose, it is necessary to reduce the unit size and increase the power that can be transmitted by units of the same size.

Further, in cold regions such as North America, traction characteristics at low temperatures are required, so that the viscosity of the traction oil is required to be further reduced. On the other hand, lowering the viscosity of oil lowers the traction characteristics at high temperatures, so it was necessary to make both low temperature characteristics and high temperature characteristics compatible.

[0006]

By the way, in order to improve the traction characteristics, a fine concavo-convex shape is formed on the rolling surface of the rolling element. However, since the traction drive is used under a very high surface pressure, the projections of the unevenness formed on the rolling surface are slightly depressed during use, and the depth of the unevenness is reduced due to some wear. . Since the reduction of the uneven depth affects the traction characteristics, it has been demanded to minimize the change of the uneven depth and maintain the high traction characteristics for a long period of time.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional circumstances, and is excellent in traction characteristics capable of transmitting a large amount of power, and also exerts such excellent characteristics without changing with time. An object of the present invention is to provide a rolling element for a traction drive and a method for manufacturing the same.

[0008]

According to a first aspect of the present invention, there is provided a rolling element for a traction drive, in which the traction drive rolling element transmits power through traction oil between rolling surfaces. Regarding the fine surface shape of the rolling surface that transmits the power of either one of the driven elements on the driven side, the cross-sectional curved shape obtained by using a surface roughness meter without passing through a filter is a concave portion that is a groove. It is a shape in which convex parts that are ridges are alternately arranged, and the shape of the convex part above the center line of the cross-sectional curve is a roughly trapezoidal shape with rounded corners, a roughly crowning shape, a roughly elliptic arc shape, a roughly It has either a sinusoidal shape or a roughly triangular shape with a rounded top, and λ / AMP, which is the ratio of the wavelength λ of the unevenness to the AMP that is half the groove depth, is 50 or more and 400 or less. Then, the rolling surface of the other rolling element is made smooth, and the relationship between the surface hardness Hx of the rolling portion of one rolling element and the surface hardness Hy of the rolling portion of the other rolling element is expressed as
The configuration is such that Hx> Hy.

In the above construction, the surface hardness Hx, Hy of the rolling part is the hardness Hv measured by JIS Z 2244 "Vickers hardness test method", and the rolling element having unevenness on the rolling surface is used. H when measuring the surface hardness of
Let v be Hx, and Hv when the surface hardness of the rolling element having a smooth rolling surface is measured is defined as Hy.

Further, as the shot peening processing according to claim 5, a very small diameter shot peening processing (WP
C: Wide Peaning and Cleaning) is performed, and the projection conditions are not particularly limited, but for example, a projection material having an average particle size of about 50 μm and a hardness of 750 Hv or more at a high speed of 100 m / s or more. To project.

Further, as the combination of the material used for the rolling element and the heat treatment at the time of manufacturing the rolling element, a combination of case-hardening steel material and carburizing quenching and tempering heat treatment, a combination of case hardening steel material and carbonitriding quenching and tempering heat treatment, bearing steel material And quenching and tempering heat treatment, bearing steel material and carburizing quenching and tempering heat treatment combination, and bearing steel material and carbonitriding quenching and tempering heat treatment combination are preferably selected. Although obtained, the production method according to the present invention is not particularly limited to these.

[0012]

According to the rolling element for a traction drive according to claim 1 of the present invention, a large traction force can be generated while keeping the metal contact small, and a large motive power can be transmitted. It is possible to provide a rolling element for a traction drive having excellent characteristics.

Further, in particular, by setting the ratio λ / AMP, which is the ratio of the wavelength λ of the unevenness to the AMP which is half the groove depth, to 50 or more and 400 or less, the change in the depth of the unevenness with time is suppressed, and the traction is reduced. The force can be output stably and continuously, and the durability can be dramatically improved. Furthermore, the relationship between the surface hardness Hx of the rolling portion of one rolling element and the surface hardness Hy of the rolling portion of the other rolling element is expressed as Hx.
By setting> Hy, it is possible to suppress the deformation of the rolling element having unevenness on the surface and to extremely reduce the change in the depth of unevenness over time, and to stably output a large traction force continuously. Become.

According to the rolling element for traction drive of the second aspect of the present invention, the same effect as that of the first aspect can be obtained, and at least the depth of at least 20 μm from the surface of the rolling portion of the rolling element. In Table 1, the relationship between the surface hardness Hx of one rolling element having unevenness on the rolling surface and the surface hardness Hy of the other rolling element having a smooth rolling surface is Hx> Hy It is possible to provide a rolling element for a traction drive that can further reduce the change with time and stably output a large traction force continuously.

According to the rolling element for traction drive of the third aspect of the present invention, the same effects as those of the first and second aspects can be obtained, and the surface hardness of the rolling element having unevenness on the rolling surface is obtained. By setting Hx to 850 or more, the deformation of the rolling element can be more reliably suppressed, the change in the depth of the unevenness with time can be further reduced, and a large traction force can be stably and continuously maintained. The effect of improving the durability of being able to output is brought about.

According to the rolling element for traction drive of the fourth aspect of the present invention, the same effects as those of the first to third aspects can be obtained, and the rolling element is applied to the half toroidal type continuously variable transmission. can do. That is, it is sandwiched between the input disc and the output disc, each of which has a rolling surface having a toroidal curved type annular concave surface shape, and the annular concave rolling surface of the input disk and the output disk which are arranged to face each other. By using a power roller etc. that has a rolling surface that forms an annular convex surface and can tilt the roller shaft, it is possible to transmit a large amount of power, and it is also possible to reduce the unit size and weight. Furthermore, it is possible to increase the output per unit volume and unit weight.

According to the method of manufacturing a rolling element for a traction drive according to a fifth aspect of the present invention, the rolling surface is formed by subjecting one surface of the rolling element to shot peening and then forming irregularities on the surface. In addition, it is possible to obtain a traction drive rolling element having desired unevenness at low cost and with high accuracy.

According to the method of manufacturing a rolling element for a traction drive of the sixth aspect of the present invention, the rolling surface is formed by forming the unevenness on the surface of one rolling element and then subjecting the surface to shot peening treatment. In addition, it is possible to obtain a traction drive rolling element having desired unevenness at low cost and with high accuracy.

According to the method of manufacturing a rolling element for a traction drive according to a seventh aspect of the present invention, after forming irregularities on the surface of one rolling element, the convex portion is hardened by centrifugal barrel polishing or gravity-drop barrel polishing. By rolling the convex part to an arbitrary roughness while making it possible, it is possible to obtain a rolling element for traction drive with desired unevenness on the rolling surface at low cost and with high accuracy. Can be cured with high precision.

[0020]

EXAMPLES Examples of rolling elements for traction drive according to the present invention will be described in detail below together with comparative examples. The rolling element for traction drive according to the present invention is
It goes without saying that the present invention is not limited to the following examples.

First, the test method will be described. A rolling / sliding test of rolling elements (test pieces) was carried out using the 4-cylinder tester shown in FIG. The four-cylinder tester shown in the drawing has a slave shaft 51 and three spindles 53a to 53c which are arranged in parallel with each other around the slave shaft 51 and rotate via a planetary gear.
And three driving side rolling elements 54a to 54c individually supported by the respective main shafts 53a to 53c are brought into contact with the outer peripheral surface of the driven side rolling element 52 supported by the driven shaft 51. One of 53a to 53c (53a)
By applying a load to the driven-side rolling element 52, the driving-side rolling elements 54a to 54c are brought into pressure contact with the outer peripheral surface of the driven-side rolling element 52.

The pressurizing mechanism includes three pressurizing arms 55a to 55a.
55c is arranged in a T shape, each arm 55a to 55c is slidably held in the vertical direction, and a weight 56 is hung at the outer ends of the two horizontally arranged arms 55a and 55b. , The inner ends of both arms 55a and 55b are vertically stacked. In addition, the remaining one arm 55c has its one end portion superposed on the superposed portion of the horizontal arms 55a and 55b, and the other end portion provided on the rotary shaft 53a of the drive side rolling element 54a. It is in contact with 57.

In the four-cylinder rolling tester, in the pressurizing mechanism, the weight of the left and right weights 56 is set to the arms 55a to 55a.
The drive side rolling elements 54a to 54c are brought into pressure contact with the outer peripheral surface of the driven side rolling element 52, and the torque sensor provided on the driven shaft 51 of the driven side rolling element 52 is used. The traction coefficient can be calculated by measuring the torque generated in the slave shaft 51.

In the test of this embodiment, the slip ratio is 1.5.
%, Average slip speed: 30 m / s, average shaft speed: 10
000 rpm, the main shafts 53a to 53c and the slave shaft 51 are evenly differentiated to keep the slip speed constant.
The traction oil set at 0 ° C. was supplied at a rate of 2 L / min from the inlet in the rotational direction, and continuously operated for 1 hour. The number of loads at this time is 1.8 × 10 6.

Next, Examples 1 to 3 and 6 to 8 shown in Table 1 will be described. The driven-side rolling element 52 has a diameter of 60 mm and a thickness of 10 mm, and has a flat cylindrical rolling surface. In this example and the comparative example, JIS SCM42, which is chromium molybdenum steel, is used.
0 steel was carbonitrided, quenched and tempered under the conditions shown in Fig. 3 and the rolling surface was ground, and then a pneumatic shot peening machine was used to use steel balls with a mean particle size of 50 µm and a hardness of 750 Hv as the shot material. Then, the distance between the nozzle and the work (φ60 cylindrical outer peripheral surface) was set to 100 mm, and the projection was performed at an air pressure of 5 kgf / mm ^{2 with} a projection nozzle having a diameter of 5 mm.

At this time, the head is swung so as to reciprocate in the axial direction of the nozzle so that the amount of projection is substantially uniform with respect to each position on the outer peripheral surface of the φ60 cylinder, and the work is rotated by 1 r.
It was rotated at pm and projected for 180 seconds. afterwards,
Grooves are cut on the rolling surface using a polycrystalline c-BN cutting tool, and then the protrusions are cut off with tape wrap to control the groove depth and spacing to the desired values. Then, the desired fine surface morphology of the uneven shape obtained by alternately arranging the groove portions and the ridge portions was obtained.

[0027]

[Table 1]

In addition, in the cross-section curve obtained by cutting the concave portion which is the groove of the rolling element and the convex portion which is the protruding portion by a plane perpendicular to the continuous direction of the concave portion and the convex portion, the convex portion above the center line is formed. The shape of the part is a roughly crowning shape, and the wavelength of unevenness λ
And λ / AMP, which is the ratio of AMP at half the groove depth, have the specifications shown in Table 1, respectively. The shape of the first embodiment is shown in FIG. 4 as an example of the shape of the recess. Also in the other Examples 2, 3 and 6 to 8, the shape of the recess was almost the same as that in FIG.

On the other hand, the three outer driving side rolling elements 54a-5
For 4c, the diameter was 60 mm, the thickness was 10 mm, and the rolling surface was a cylindrical shape having a crowning shape with R = 5 mm. In this case, a JIS SCM420 steel, which is a chrome molybdenum steel, is carbonitrided, quenched and tempered under the conditions shown in FIG. 3, and the center line average roughness Ra is obtained by superfinishing after grinding the rolling surface. 0.02μ
m, and the maximum height Ry was 0.12 μm. As for the other cylinder, this cylinder was used in all of the Examples and Comparative Examples.

Next, a fourth embodiment will be described. In this example, the same construction method as in Examples 1 to 3 and 6 to 8 was used, but the process was changed. That is, diameter = 60m
m, thickness = 10 mm (a chrome molybdenum steel JIS SCM420 steel was carbonitrided and quenched and tempered under the conditions shown in FIG. 3) was used. A BN cutting tool is used to cut a groove on the rolling surface, and then a pneumatic shot peening machine is used to use a steel ball having an average particle size of 50 μm and a hardness of 750 Hv as a projection material, and a nozzle-work (φ60 cylinder outer periphery) surface)
The distance was set to 100 mm, and projection was performed at an air pressure of 5 kgf / mm ^{2 with} a projection nozzle having a diameter of 5 mm.

At this time, the head is swung so as to reciprocate in the direction of the nozzle in the axial direction so that the amount of projection is substantially uniform with respect to each position on the outer peripheral surface of the φ60 cylinder, and the work is rotated by 1 r.
It was rotated at pm and projected for 180 seconds. afterwards,
The tape wrap is used to scrape off the protrusions and control them to achieve the desired groove depth and spacing, and to create the desired fine surface irregularities on the rolling surface by arranging grooves and ridges alternately. Obtained.

In addition, in a sectional curve obtained by cutting the concave portion which is the groove of the rolling element and the convex portion which is the protruding portion by a plane perpendicular to the continuous direction of the concave portion and the convex portion, the convex portion above the center line is formed. The shape of the part is a roughly crowning shape, and the wavelength of unevenness λ
Λ / AMP, which is the ratio of AMP to half the groove depth, has the specifications shown in Table 1. The shape of the recess was similar to that of Example 1 in FIG.

Next, a fifth embodiment will be described. In this embodiment, a cylinder having a diameter of 60 mm and a thickness of 10 mm (JIS SCM420 steel, which is chrome molybdenum steel, is shown in FIG.
(Uses steel that has been carbonitrided, quenched, and tempered under the conditions shown in)
On the other hand, after grinding the rolling surface, a groove is cut on the rolling surface with a polycrystalline c-BN cutting tool, and then the surface is hardened by a centrifugal barrel polishing machine, and the desired unevenness depth is obtained. Then, the treatment was performed so as to obtain the desired spacing, shape and shape. The barrel conditions are 180 rp using HAS polishing stone manufactured by Tipton.
m, and the time was controlled so as to obtain a desired unevenness depth.

At this time, in the cross-section curve obtained by cutting the concave portion which is the groove of the rolling element and the convex portion which is the protrusion on a plane perpendicular to the continuous direction of the concave portion and the convex portion, the cross-section curve above the center line is formed. The shape of the convex portion is roughly a crowning shape, and λ / AMP, which is the ratio of the wavelength λ of the unevenness and the AMP of half the groove depth, is shown in Table 1.
The specifications are shown in. The shape of the recess is shown in FIG.
Was similar to.

Next, Comparative Examples 1 to 4 will be described. For the driven side rolling element 52, diameter = 60 mm, thickness = 1
The rolling surface was 0 mm, and the rolling surface was flat. In these examples and comparative examples, JIS SCM420 steel, which is chromium molybdenum steel, was carbonitrided, quenched and tempered under the conditions shown in FIG. 3, and after rolling the rolling surface, a polycrystalline c-BN cutting tool was used. Groove to the rolling surface by using, and then the tape wrap is used to scrape off the convex portion, and the groove surface and the ridge portion are alternately arranged on the rolling surface to obtain the desired unevenness depth and spacing. The surface topography was obtained. No curing treatment was carried out.

At this time, in the cross-section curve obtained by cutting the concave portion, which is the groove of the rolling element, and the convex portion, which is the ridge, by a plane perpendicular to the continuous direction of the concave portion and the convex portion, the center line of the wavy contour line thereof. The shape of the convex portion on the upper side is approximately a crowning shape, and is the ratio of the wavelength λ of the unevenness to the AMP that is half the groove depth λ.
/ AMP has the specifications shown in Table 1, respectively. The shape of the recess was similar to that of Example 1 in FIG.

Next, the evaluation result will be described. FIG. 5 shows an example of the result of shape measurement near the rolling portion after the test of Example 1. For this shape measurement, Surfcom 1400A, which is a surface roughness shape measuring instrument manufactured by Tokyo Seimitsu Co., Ltd., was used. In the figure, and are non-rolling parts, and are rolling parts. FIG. 5 is an example in which the groove depths at the positions of are summarized.

The groove depth change of each Example and Comparative Example was measured in the same manner, and the value obtained by subtracting the groove depth of the rolling portion from the average value of the non-rolling portion and the average value of the rolling portion was used as the variation amount of the groove depth. Table 1
Summarized in.

As is clear from the results shown in Table 1, the amount of change in groove depth of the example is smaller than that of the comparative example. That is, in this embodiment, it is possible to suppress the performance change due to the decrease of the groove depth, and to stably and continuously exert a large traction force. On the other hand, in Comparative Examples 1 to 4, the groove depth change amount is large, and in this case, the result is expected that the traction coefficient decreases with time and a good traction coefficient cannot be maintained.

[Brief description of drawings]

FIG. 1 is an explanatory cross-sectional view showing the basic configuration of a traction drive type continuously variable transmission.

FIG. 2 is an explanatory diagram showing an outline of a four-cylinder rolling tester used for investigating the surface texture of the rolling surface of the rolling element for traction drive.

FIG. 3 is a graph showing a temperature pattern of heat treatment in the method for manufacturing a rolling element for a traction drive according to the present invention.

FIG. 4 is a graph showing the results of shape measurement in the vicinity of the rolling portion of the rolling element for traction drive according to Example 1 of the present invention before the test.

FIG. 5 is a graph showing the results of shape measurement in the vicinity of the rolling portion after the test of the rolling element for traction drive according to the present invention.

[Explanation of symbols]

1 Traction drive type continuously variable transmission 2 input axes 3 input discs (rolling elements) 4 output shafts 5 Output disc (rolling element) 6 Power roller (rolling element) 51 slave axis 52 Driven side rolling element 53a-53c Spindle 54a to 54c Drive side rolling element

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Yoshiteru Yasuda             Nissan, Takaracho, Kanagawa-ku, Yokohama-shi, Kanagawa Nissan             Inside the automobile corporation F term (reference) 3J051 AA03 BA03 BD02 BE09 CB07                       EC07 FA02

Claims (7)

[Claims] 1. In a rolling element for a traction drive that transmits power via traction oil between rolling surfaces, a surface fineness of a rolling surface that transmits power of either one of a driving side and a driven side. Regarding the shape, the cross-sectional curve shape obtained by using a surface roughness meter and obtained without passing through a filter is a shape in which concave parts that are grooves and convex parts that are ridges are alternately arranged, and the center of the cross-sectional curve The shape of the convex portion above the line is one of a roughly trapezoidal shape with rounded corners, a roughly crowning shape, a roughly elliptical arc shape, a roughly sine wave shape, or a roughly triangular shape with a rounded top, and the unevenness Λ / A, which is the ratio of the wavelength λ of the
MP is 50 or more and 400 or less, on the other hand, the rolling surface of the other rolling element is made smooth, and the surface hardness Hx of the rolling portion of one rolling element and the rolling surface of the other rolling element of the other rolling element. A rolling element for a traction drive, wherein the relationship with the surface hardness Hy is Hx> Hy. 2. The rolling element of the rolling element is at least 2 from the surface.
At depths up to 0 μm, the surface hardness relationship is expressed as Hx>
The rolling element for a traction drive according to claim 1, wherein the rolling element is Hy. 3. The surface hardness Hx of the rolling portion of one rolling element is set to Hv850 or more.
Or the rolling element for traction drive described in 2. 4. The input side and the output side, wherein the driving side and driven side rolling elements are constituent elements of a half toroidal type continuously variable transmission, and each of which has a toroidal curved surface type rolling surface having an annular concave surface shape. It is selected from at least two of a disk and a power roller which has a rolling surface having an annular convex surface shape sandwiched between the rolling surfaces of the disks arranged to face each other and has a roller shaft tiltable. The rolling element for traction drive according to any one of claims 1 to 3. 5. When manufacturing the rolling element for traction drive according to claim 1, shot peening is applied to the surface of one rolling element, and then irregularities are formed on the surface. And method for manufacturing rolling elements for traction drive. 6. When manufacturing the rolling element for traction drive according to any one of claims 1 to 4, after forming irregularities on the surface of one rolling element, shot peening treatment is applied to the surface. And method for manufacturing rolling elements for traction drive. 7. When manufacturing the rolling element for a traction drive according to any one of claims 1 to 4, after forming unevenness on the surface of one rolling element, it is made convex by centrifugal barrel polishing or gravity drop type barrel polishing. A method for manufacturing a rolling element for a traction drive, characterized in that the convex portion is finished to have an arbitrary roughness while curing the portion.